HOARY CRESS: Still On The Hit List In Butte County | TSLN.com

HOARY CRESS: Still On The Hit List In Butte County

Mature hoary cress in full bloom illustrates why it is called White Top. The invasive weed can take over thousands of acres if left to grow unchecked. It propagates both by a network of roots and by prolific seed production. Plants range from eight inches to three feet tall. Photo by Jan Swan Wood.

Noxious weeds are an increasingly serious problem all over the country. New “introduced” species and native species in new areas combine to make weed control a challenge. Butte County in South Dakota has a grant to help ranchers and farmers contend with one of the serious noxious weeds in the area, and a recent meeting was held to explain the funding and how to properly use the chemical being offered.

On April 7, Butte County Weed and Pest held two meetings, a lunch time meeting in Nisland, South Dakota and a supper meeting in Belle Fourche, South Dakota. Area farmers and ranchers were invited and heard information about hoary cress, a perennial noxious weed, and how to spray to try to control it. Clint Pitts, Weed and Pest Board member opened the meeting and introduced fellow board members Don Adams and Bill Erk. Also present to share information were Mike Stenson, South Dakota Department of Agriculture, Meghan Foos, CBH Cooperative agronomy specialist, Joe Varilek, area manager for Van Diest Supply Company, and Andy Canham from Mid Dakota Vegetation Management.

Hoary Cress is designated a noxious weed and is of the mustard family. It’s also known as White Top and Perennial Peppergrass and is a native of Eurasia that arrived in the United States in contaminated seed in the early 1900s. It is a relatively long lived plant with rhizomatous roots which spread in a network underground. The network of roots can create over 450 shoots and cover an area 12 feet in diameter in one year. A single three year old plant can product 1200-4800 seeds per year with the seeds surviving up to seven years in the soil.

Hoary cress is adaptive to many soil types and thrives in alkaline soils. It is very drought resistant with roots that reach from 30 inches to 30 feet in depth. Since it spreads both by root and seed, it can take over a large area in a short amount of time. The cold season perennial is usually the first forb that leafs out in late March and early April and will use all of the available moisture and choke other plants out.

“Hoary cress contains glucosinolates which irritate the mucous membranes in the mouth of the animals, causing it to graze less. It also passes through into the milk, affecting nursing calves and lambs as well. Fortunately, livestock will only graze it when forced to due to lack of other forage.” Meghan Foos, CBH Cooperative agronomy specialist

The seed from hoary cress is spread by water, wind, livestock, wildlife, vehicles, machinery, hay bales, and even muddy boots. It can contaminate mulch, feed, grass and crop seed, top soil, gravel, and be transported in all of them. It’s invasive and persistent nature can lead to substantial losses on both grazing and hay land, and both production volume and feed quality are affected.

Hoary cress isn’t a poisonous weed, but if ingested, can cause problems, states Foos. “Hoary cress contains glucosinolates which irritate the mucous membranes in the mouth of the animals, causing it to graze less. It also passes through into the milk, affecting nursing calves and lambs as well. Fortunately, livestock will only graze it when forced to due to lack of other forage.”

Similar in appearance to another member of the mustard family called penny cress, the difference can be clearly seen when a closer examination is done. Hoary cress has a blue/gray tint to the leaf, while the leaf of penny cress is a bright green. One easy way to tell whether an established plant is hoary cress or penny cress is to pull it up. If it pulls with difficulty and only a little of the root comes up, it is hoary cress. If it pulls easily and the whole root comes up, it is penny cress.

Controlling hoary cress requires careful scouting for plants as soon as they start to grow. Andy Canham, a weed management specialist, says “Make sure you’re finding it early. Keep checking for it and be ready to spray as many times as needed.” He adds, “Spraying it when it is growing rapidly gets the best control of the plant. Once it has bloomed, spraying won’t have much affect, though marking areas where it blooms is a good idea for future spraying.”

Foos concurs, saying “Spray early in the spring or again during a wet fall when new seeds are sprouting and growing rapidly.”

Butte County’s grant for spraying hoary cress is for the use of Escort XP, a DuPont product. Escort is safe to use on grazing pasture but caution must be used if spraying near legumes, such as alfalfa. It does have a residual of 18 months to three years, so planting alfalfa after spraying a field with Escort XP is not recommended.

The formula for hand or small tank spraying was shared by Foos and is as follows:

.5 oz Escort XP to 64 oz warm water

2 oz of Surfactant

1 tsp household ammonia

Mix well.

Add 8 oz of this mixture to 3-4 gallons of water and spray within 70 hours of mixing.

“Making sure that your Escort is mixed is critical,” says Foos. “If it’s still in the granule form when you’re done you’ve wasted your time. Warm water really helps to dissolve it so use that if you have it available. Always remix after the spray has set for a while.”

Joe Varilek stresses that surfactants are critical. “Surfactants make your chemical work much better. Spend your money right and use a product that will stick to the leaves. Premier 90 works very well and also prevents foaming in the sprayer. It costs about 50 cents per acre, so is very economical, plus it works very well with the chemicals used for hoary cress.”

Stenson added, “Spraying is the only control for hoary cress. There is no biological control like insects, mowing isn’t effective at all, and prevention is only part of the formula. If you don’t overgraze pastures, hoary cress has a harder time getting established.”

When spraying, be sure to spray in a wide area beyond the furthest detected plants. With the root system of hoary cress able to spread rapidly, spraying at least three feet beyond the edge of the patch is critical. Go back over the area repeatedly to check for new growth outside of the sprayed area as well. Spraying on days without wind will also have a better outcome with less chance of drift onto susceptible plants like alfalfa.

Landowners in Butte County can apply for no cost Escort XP by contacting the Butte County Weed and Pest office at 605-456-1313 for the form, which, when filled out needs to be returned to the office right away. The chemical is available on a first come, first served basis, and Bill Erk will deliver the product to the landowners.

If the landowner is unable to spray themselves, they can contact Andrew Canham at 605-530-8089 to set up an appointment on his list.

With hoary cress spreading across the state, prevention is easier than eradication, and hitting it hard at the first sign of an invasion is critical. Familiarizing yourself with the appearance of the plants in the early stages of growth is also necessary, since once it’s in the bloom stage, it’s too late.

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